Method in the preparation of progressive-burning smokeless powder, and product thereof



Patented Feb. 21, 1939 UNITED STATES PATENT OFFICE Ellsworth S. Goodyear, Kenvil, N. J., assignor to Hercules Powder Company, Wilmington, DeL, a corporation of Delaware No Drawing. Application July 6,1937,

Serial No. 152,269

20 Claims.

This invention relates to an improved method in the preparation of progressive-burning smokeless powder and more particularly to an improved method of coating smokeless powder with a de- 5 terrent material and to smokeless powder coated with'a deterrent material.

As is well known, in order to render possible close control of the burning rate of smokeless powder and produce a high velocity of the projectile without high breech pressures, it has been customary to coat the grains of the smokeless powder with a deterrent material, explosive or non-explosive, which will retard the initial burning rate of the powder grains. Such coating material penetrates the powder grains more or less, so that as the powder burns, the successively exposed surfaces contain gradually less and less of the deterrent material, thus causing the combustion of the grains to proceed with increasing speed.

In order to effect. the coating of smokeless pow- .der grains with a deterrent material, numerous processes have been devised, e. g., using dinitrotoluene as the deterrent material, powder grains coated with dinitrotoluene are subjected to heat, with or without the presence of moisture or water. By another method, the powder grains are coated by treatment with a solution of dinitrotoluene in benzene, the benzene evaporated, and penetration of the dinitrotoluene into the grain of powder obtained by immersing the coated powder grains in a hot water bath for several hours or several days. By still another method, using as the deterrent material, a mixture of dimethyldiphenyl .urea and dinitrotoluene, or dimethyldiphenyl urea. alone, the powder grains and deterrent material are covered with water, or merely wet with water, and after mixing, heat is applied for varying periods. By still another method the powder grains are surface treated by an alkyl phthalate, either in solution or in an aqueous emulsion.

Treatment of smokeless powder grains to render their combustion progressive by applying thereto a deterrent by methods heretofore known,

while producing the results to a desired degree.

has been open to a number of objections. The deterrents heretofore used have, for example, been more or less good solvents for the nitrocellulose of the smokelesspowder, and consequently, even if applied on the surface of the powder grain, have penetrated to a depth into the powder grain depending upon the conditions of treatment, e. g., a longer time of heating of the powder grains with the deterrent or solution of the deterrent causing a deeper penetration of the deterrent into the powder grains than would otherwise be the case.

In more recent work on this problem it has been found that powder grains coated with materials which are non-volatile, non-explosive and non- 5 solvents for the nitrocellulose in the powder but compatible therewith have definite advantages over previously known deterrent materials. According to this method a deterrent material such as butyl acetyl ricinoleate, hydrogenated methyl 10 abietate, ethylene glycol terpinene maleate, wood rosin, etc., is applied to the powder in solution in a volatilizable solvent which is a non-solvent for the smokeless powder. The powder and the solution containing the deterrent are tumbled to- 15 I gether at the temperature desired, depending on the type of powder, and after uniform distribution of the deterrent material on the powder grain, the volatile solvent is eliminated by evaporation. works very satisfactorily with many types of powder, butwhere a very heavy deterrent layer is desired. it is advisable to have more adequate penetration of the deterrent into the grain than obtained by following the above procedure. 25 Moreover, when a heavy deterrent layer is desired there is a tendency to produce a greasy or resinous surface on the grain. Such a surface is not readily glazed with graphite to produce a free-flowing powder.

Now in accordance with my invention I may apply the deterrent material, which is a nonsolvent for the nitrocellulose in the powder but compatible therewith, admixed with either a. volatile or non-volatile solvent for said nitrocel- 35 lulose and avoid the above mentioned greasiness. The presence of the solvent softens the outside of the powder grain and causes the mixture of S01 vent and non-solvent material to penetrate into the grain, the degree of penetration being con- 40 trolled by the ratio of solvent to non-solvent-material. When a non-volatile solvent is used it remains in the powder and has a deterrent action on the smokeless powder over and above that produced by the non-solvent deterrent. Alter- 45 natively, when a volatile solvent is used, it is eliminated by drying and has no further effect on' the, powder.

In accordance with my invention, I may, if so desired, extend the mixture of a volatile or non- 5 volatile solvent and the non-solvent deterrent with a volatile vehicle which is not a solvent for the smokeless powder grains such as benzene, ethyl alcohol, petroleum. spirits etc., in order to render the above said mixture more fluid and 55 It has been found that this method 20 thus cause it to come into more intimate contact with the powder and then subsequently remove this vehicle by evaporation. Alternatively I may extend the mixture of a volatile ornon-volatile solvent and the non-solvent deterrent by forming an aqueous emulsion thereof, using a suitable emulsifying agent. Furthermore, I may also form an aqueous emulsion of the volatile vehicle extended mixture of the first procedure mentioned above. The particular method used for rendering the above mentioned mixture more fluid will depend on which is more convenient and desirable for the particular deterrent and smokeless powder in question.

In using my process, it may also be desirable to add water near the end of my coating procedure in order to prevent the grains of powder from adhering to each other. Near the end of the coating process a very concentrated solution .remains on the powder grains, which on further evaporation causes the coating material to be deposited on the surface of the powder grain resulting in the adherence of the grains to each other. Now I have found that if water is added at this stage,-that is, just before serious clustering begins, that each grain will be surrounded by a film of water which greatly reduces the stickiness of the grains. Heating can then be continued either in the sweetie barrel or in the dry house to cause the penetration of this surface material into the grain and thus avoid the forma tron of clusters.

As examples of deterrents which I may utilise to coat the grains of smokeless powder in accordance with this invention I may use the alkyl esters of the fatty acids, as, alkyl esters of ricinoleic -acid, alkyl esters of polymerized ricinoleic acid, etc.; terpene phthalates, rosin esters, as monohydric esters of abietic acid, polyhydric alcohol esters of abietic acid, monohydric alcohol esters of pimaric acid, polyhydric alcohol esters of pimaric acid. Synthetic lacquer resins as the modified or unmodified polyhydric alcohol-polybasic acid resins (alkyds, rezyls), phenol dorm-=- aldehyde type resins, etc.; rosins, as wood rosin, gum rosin, etc.; hydrogenated .rosins, as hydrogenated wood rosin, hydrogenated gum rosin, etc.; and the like. Thus I may use butyi risinoleate, butyl acetyl ricinoleate, butyl ester of polymerized ricinoleic acid, dibornyl phthalate, methyl abietate, ethyl abietate, hydrogenated methyl abietate, hydrogenated ethyl abietate, ester gum, hydrogenated ester gum, modified or unmodified glycerol-phthalate resin, oil modified phenol-formaldehyde type resins, glycerol sebacate, glycol sebacate, glycerol-glycol sebacate, modified or unmodified ethylene glycol terpinene maleic anhydride resins, modified or unmodified diethylene glycol terpinene maleic anhydride resins, modified or unmodified triethylene glycol terpinene maleic anhydride resins, modified or unmodified glycerol terpinene maleic anhydride resins, etc.

As examples of the non-volatile solvent materials which I may use with the above mentioned deterrents, I may use the alkylphthalates as for example, diethyl phthalate, dibutyl phthalate, diamyl phthalate, etc.; alkyl phthalyl alkyl glycollates, as for example, butyl phthalyl butyl glycollate, ethyl phthalyl ethyl glycollate, etc.; substituted urea, as forexample, symmetrical diethyl diphenyl urea, symmetrical dimethyl diphenyl urea, symmetrical ethyl methyl diphenyl urea, etc.; alkyl tartrates such as dibutyl tartrate, etc.;

alkyl citrates such as triethyl citrate, etc.; adipates such as cyclohexanol adipate.

As examples of the volatile solvent materials which I may use with the above mentioned deterrents, I may use ethyl acetate, butyl acetate. mixtures of alcohol and ether and any others having a solvent effect on the nitrocellulose in the smokeless powders and having a boiling point from about 35 C. to about 180 C., preferably from about 70 C. to about 130 C.

As illustrative of my invention, I may coat 100 parts by weight of a tubular grain rifle powder with between about 0.5 and about 10 parts by weight of a mixture comprising 25% to 95% of a deterrent, non-volatile and non-explosive and which is a non-solvent for the nitrocellulose but compatible therewith and 5% to 75% of a nonvolatile non-explosive solvent plasticizer for the nitrocellulose, said mixture being dissolved in 3 parts to 50 parts by weight of a volatile vehicle having substantially no solvent action on the hitrocellulose. In place of the non-volatile nonexplosive solvent plasticizer, I may also use a volatile solvent for the nitrocellulose.

Alternatively, I may coat 100 parts by weight of a tubular grain smokeless powder suitable for use in high powered rifies with between about 0.5 part to about 10 parts by weight of a mixture comprising 25% to 95% of a deterrent, non-volatile and non-explosive and which is a non-solvent for the nitrocellulose but compatible therewith and 5% to 75% of a non-volatile, non-explosive solvent plasticizer for the nitrocellulose, said mixture being emulsified in 3 to 50 parts by weight of an aqueous solution of water-soluble carbohydrate ether, such as for example, methyl cellulose. In place of the non-volatile, non-explosive solvent plasticizer, I may also use a volatile solvent for the nitrocellulose.

As a further illustration, I may coat 100 parts by weight of a tubular grain smokeless powder, suitable for use in high powered rifles with between about 0.5 part to about 10 parts by weight of a deterrent non-volatile and non-explosive which is a non-solvent for the nitrocellulose but compatible therewith dissolved in 1 part to 20 parts by weight of a volatile solvent for nitrocellulose and 3 parts to 50 parts by weight of a volatile vehicle which is a non-solvent for the powder. vent volatile vehicle, I may use 3 parts to 50 parts by weight of an aqueous solution of methyl cellulose and apply the above mixture in the form of an emulsion.

As a specific example of the carrying out of the process involving my invention, and producing my improved product, 906 parts by weight of smokeless powder containing 20% nitroglycerine are pressed through a 0.045 inch die having a 0.015 inch pin, the resulting strands being out into 21 pellets per inch. These smokeless powder grains are placed in a cold sweetie barrel and to them are added 14.? parts by weight of centralite and 14.7 parts by weight of dibornyl phthalate dissolved in Bl parts by weight of ethyl alcohol and 126 parts by weight of ethylene dichloride at a temperature of about 70 C. to about C., and the mixture tumbled in a closed sweetie barrel for about 1% hours at a temperature of (2., this temperature having been attained during the first 15 minutes. After coating, the powder is dried for about three days at approximately 55 C., glazed with graphite and screened to remove any coarse or fine material. As a further specific example of the carrying Alternatively, instead of the non-sol- I out of the process involving my invention 906 parts by weight of smokeless powder containing 20% nitroglycerine are pressed through a 0.045 inch die having a 0.015 inch pin, the resulting strands being cut into 11 pellets per inch. These smokeless powder grains are placed in a cold sweetie barrel and to them are added 27.2 parts by weight of an alkyd resin and 18.1 parts by weight of butyl phthalyl butyl-glycollate dissolved in 163 parts by weight of ethyl alcohol, the mixture tumbled in a closed sweetie barrel for about 1 hour, the temperature having been brought to about 90 C. during the first half hour. After coating, the powder is dried for about three days at approximately 55 C., glazedwith graphite and screened to remove any coarse or fine material.

As further specific examples of the carrying out of the process involving my invention the same amount of powder of the same composition as in the previous example is coated in the same manner with the following combinations:

(1) 13.6 parts by weight of castor oil and 31.7 parts by weight of diethyl phthalate dissolved in 163 parts by weight of ethyl alcohol.

(2). 27.2 parts by weight of butyl acetyl ricinoleate and 18.1 parts by weight of dibutyl tartrate dissolved in 163 parts by weight of ethyl alcohol.

(3) 22.7 parts by weight of butyl acetyl ricin-' oleate and 22.7 parts by weight of triethyl citrate dissolved in 163 parts by weight of ethyl alcohol.

(4) 45 parts by weight of hydrogenated methyl abietate dissolved in 45 parts by weight of butyl acetate, the resulting solution emulsified in 50 parts by weight of a 4% by weight solution of methyl cellulose in water and adding an additional 100 parts by weight of water.

(5) 45 parts by weight of glycerol abietate dissolved in 45 parts by weight of butyl acetate, the resulting'solution emulsified in 50 parts by weight of a 4% by weight solution of methyl cellulose in water and adding an additional 100 parts by weight of water.

(6) 45 parts by weight of glycerol abietate dissolved in 45 parts by weight of butyl acetate and 163 parts by weight of ethyl alcohol.

(7) 45 parts by weight of hydrogenated methyl abietate dissolved in 45 parts by weight of butyl acetate and 163 parts by weight of ethyl alcohol.

(8) 45 parts by weight of hydrogenated methyl abietate dissolved in 45 parts by weight of methyl acetate and 163 parts by weight oi. ethyl alcohol.

(9) 22.7 parts by weight of hydrogenated methyl abietate and 22.7 parts by weight of diethyl phthalate dissolved in 25 parts by weight of benzol, the resulting solution emulsified with 50 parts by weight of a 4% aqueous solution of methyl cellulose and 100 parts by weight of water added to the emulsion.

(10) 18.1 parts by weight of butyl acetyl ricinoleate and 27.2 parts by weight of symmetrical diethyl diphenyl urea dissolved in 50 parts by weight of benzol, the resulting solution emulsified with 50 parts by weight of a 4% aqueous solution of methyl cellulose and 100 parts by weight of water added to the emulsion.

(11) 18.1 parts by weight of triethylene glycol terpinene maleic anhydride resin and 27.2 parts by weight of butyl phthalyl butyl glycollate dissolved in 30 parts by weight of benzol, the resulting solution emulsified with 50 parts by weight of a 4% aqueous solution of methyl cellulose and 100 parts by weight of water added to the emulsion.

After coating the powders in all the above examples, they are dried for approximately three days at a temperature of about 55 0., glazed with graphite and screened to remove any coarse or fine material.

The temperature of coating may be varied between about 20 C. and 100 C. and the time 01 coating may be varied between 15 minutes and six hours depending upon the coating combination, the type of powder coated and the results desired. I prefer to use a temperature between about 60 C. and about 95 C. and to treat the powder in the sweetie barrel from 45 minutes to 2 hours.

It will be understood that where I have referred to a compound as being a non-solvent for nitrocellulose, I mean a compound which, by reason of its relatively low content of chemical groups which are known to promote solvent action, its high molecular weight, its high viscosity at temperatures to which the compoundmay be subjected, or its. structural arrangement, does notv dissolve nitrocellulose of the degree of nitration used in a particular case, at a measurable rate of solution.

By coating smokeless powder according to my process as illustrated in the above examples, I can effectively control the penetration of the deterrent and can thus eliminate the disadvantages of coating with the non-solvent deterrent alone. It will be understood that I may change the ratio of non-solvent deterrent to either volatile or nonvolatile solvent to obtain the desired degree of penetration, depending upon the ballistic results desired, the amount of deterrent applied, the size of the powder grain and its composition.

It will be understood that the details and examples hereinbefore set forth are illustrative only and that the invention as herein broadly described and claimed is in no way limited thereby.

What I claim and desire to protect by Letters Patent is:

1. Method of preparation of progressive-buming smokeless powder comprising coating smokeless powder grains with an admixture of a nonvolatile, non-explosive organic material, which is a non-solvent for the nitrocellulose but compatible therewith and a solvent for said nitrocellulose.

2. Method for the preparation of progressiveburning smokeless powder comprising coating smokeless powder grains with an admixture of an alkyl ester of a higher fatty acid and a solvent for nitrocellulose.

3. Method for the preparation of progressiveburning smokeless powder comprising coating smokeless powder grains with an admixture of an alkyl ester of ricinoleic acid and a solvent for nitrocellulose.

4. Method for the preparation of progressivebuming smokeless powder comprising coating smokeless powder grains with an admixture of butylacet'yl ricinoleate and a solvent for nitrocellulose.

5. Method for the preparation of progressiveburning smokeless powder comprising coating smokeless powder grains with an admixture of a synthetic lacquer resin'and a solvent for nitrocellulose.

6. Method for the preparation of progressiveburning smokeless powder comprising coating smokelesspowder grains with an admixture of a polybasic acid-polyhydric alcohol resin and a solvent for nitrocellulose.

7. Method for the preparation of progressiveburning smokeless powder comprising coating smokeless powder grains with an admixture of a 76 cellulose.

.burning smokeless powder comprising coating smokeless powder grains with an admixture'of a lwdrogenated monohydric alcohol ester of rosin and a solvent for nitrocellulose.

10. Method for the preparation of progressiveburning smokeless powder comprising coating smokeless powder grains with an admixture of a hydrogenated methyl abietate and a solvent for nitrocellulose.

11. As a product, smokeless powder grains coated with an admixture of a non-volatile, non- I explosive organic material which is a non-solvent for nitrocellulose but compatible therewith and a substantially non-volatile solvent for said nitro- 12. As a product, smokeless powder grains coated with an admixture of an alkyl ester of a higher fatty acid and a substantially non-volatile solvent for nitrocellulose.

13. As a product, smokeless powder grains coated with an admixture of an alkyl ester of ricinoleic acid and a substantially non-volatile solvent for nitrocellulose.

14. As a product, smokeless powder grains coated with an admixture of butyl acetyl rlcinoleate and a substantially non-volatile solvent for nitrocellulose.

15. As a product, smokeless powder grains coated with an admixture of a synthetic lacquer resin and a substantially non-volatile solvent for nitrocellulose. I

16. As a product, smokeless powder grains coated with an admixture of a polybasic acidpolyhydric alcohol resin and a substantially nonvolatile solvent for nitrocellulose.

17. As a product, smokeless powder grains 20. As a product, smokeless powder grains coated with an admixture of hydrogenated methyl abietate and a substantially non-volatilesolvent for nitrocellulose.

'ELLSWORTH s. GOODYEAR. 

